Anthrax toxin fusion proteins and related methods

Abstract

The present invention provides a nucleic acid encoding a fusion protein comprising a nucleotide sequence encoding the anthrax protective antigen (PA) binding domain of the native anthrax lethal factor (LF) protein and a nucleotide sequence encoding an activity inducing domain of a second protein. Also provided is a nucleic acid encoding a fusion protein comprising a nucleotide sequence encoding the translocation domain and LF binding domain of the native anthrax PA protein and a nucleotide sequence encoding a ligand domain which specifically binds a cellular target. Proteins encoded by the nucleic acid of the invention, vectors comprising the nucleic acids and hosts capable of expressing the protein encoded by the nucleic acids are also provided. A composition comprising the PA binding domain of the native LF protein chemically attached to a non-LF activity inducing moiety is further provided. A method for delivering an activity to a cell is provided. The steps of the method include a) administering to the cell a protein comprising the translocation domain and the LF binding domain of the native PA protein and a ligand domain, and b) administering to the cell a product comprising the PA binding domain of the native LF protein and a non-LF activity inducing moiety, whereby the product administered in step b) is internalized into the cell and performs the activity within the cell. The invention also provides proteins including an anthrax protective antigen which has been mutated to replace the trypsin cleavage site with residues recognized specifically by the HIV-1 protease.

We claim: 
     
       1. A method for targeting compounds having a desired biological activity not present on native anthrax lethal factor (LF) to a specific cell population, comprising: a) administering to the cell population a first compound comprising a first protein consisting essentially of: i) the translocation domain and the anthrax lethal factor (LF) binding domain of the native anthrax protective antigen (PA) protein, and   ii) a ligand domain that specifically binds the first protein to a target on the surface of the cell population to bind the first compound to said surface; and     b) administering to the resultant cell population a second compound comprising a fusion protein or conjugate consisting essentially of: i) the anthrax protective antigen (PA) binding domain of the native anthrax lethal factor (LF) protein, chemically attached to   ii) a biological activity-inducing polypeptide to bind the second compound to the first compound on the surface of the cell population, internalize the second compound into the cell population, and effect the activity of the polypeptide therein.     
     
     
       2. A method according to claim 1, wherein the anthrax protective antigen (PA) binding domain of said second compound comprises at least the first 254 amino acid residues but less than all of the amino acid residues of the anthrax lethal factor (SEQ. ID NO: 2). 
     
     
       3. A method according to claim 1, wherein the ligand domain of said first compound is the ligand domain of the native anthrax protective antigen (PA) protein. 
     
     
       4. A method according to claim 1, wherein said second compound comprises the anthrax protective antigen (PA) binding domain of the native anthrax lethal factor (LF) protein chemically attached to a polypeptide through a peptide bond. 
     
     
       5. The method of claim 1, wherein the polypeptide of said second compound is a toxin. 
     
     
       6. The method of claim 1, wherein the polypeptide of said second compound is an enzyme. 
     
     
       7. The method of claim 1, wherein the ligand domain of said first compound is an antibody. 
     
     
       8. The method of claim 1, wherein the ligand domain of said first compound is a growth factor. 
     
     
       9. The method of claim 5, wherein the polypeptide of said second compound is Pseudomonas exotoxin A (PE). 
     
     
       10. The method of claim 5, wherein the polypeptide of said second compound is the A chain of Diptheria toxin. 
     
     
       11. The method of claim 5, wherein the polypeptide of said second compound is shiga toxin. 
     
     
       12. The method of claim 7, wherein the ligand domain of said first compound is a single chain antibody.